Method of dewaxing hydrocarbon oils



ec. 3, 1935. E, PETTY 2,023,181

METHOD 0F DEWAXING HYDROCARBON OILS Filed May 19, 1932 "ewaxea a//A'S deca/onza@ by ang A T TORNEY.

Pastas' Dea 3,1935

I 2,023,181 METHOD oF nnwziro mnocAnoN vEarl Petty, Hempstead, N. Y., assigner to Alco Products Incorporated poration of Delaware New York, N. Y., a cor- Application May 19, 1932, Serial No. 612,238

Claims. (Cl. 19H-21) My invention relates to a process of dewaxing hydrocarbon oils and more particularly to a combination process in which hydrocarbon oils are dewaxed and decolorlzed, the decolorizing steps 5 being so controlled as to effect `more emcient and complete dewaxing.

This application is a continuation in part of.

my copending application, Serial No. 557,826, .illed August i8, 1931. Y

Asphaltic coloring material is present in all crude oils. yIthas long been known that the presence oi coloringmaterials in oils retards theformation ci wax crystals. A wax distillate, for example, which is too dark-in color, will be found to' l5 have poor pressing qualities due to a lack of g crystallinestructure. It has been the practice to distill dark colored lwax distillates so that the coloring material may be removed as a res idue from thedistillation process. Most of the was is of a boiling range kwhich will enable it to be separated from the maior portion of the coloring material which has a higher boiling range t the waxes and oils from '75 seconds to lo@ seconds at 100 F.`Saybolt universal.

In higher boiling range fractions, it is impossible to remove the coloring material by distillation much as the boiling point range of the Evan is parallel to or the same asthe coloring mat er.

the well known decolorizing treating4 processes involving the use of sulphuric acid or sulphurl dioxide. The treated oil, though decolorized, will not produce crystalline waxes however, due to the presence of the viscous matter in the oil in which the waxes dissolve. Oils having a range from Gil to 150 viscosity at 210" F. always bear a large proportion of wax in an amorphous form.

As pointed out above, inasmuch as the coloring material partially dissolves the wax and tends to retard not only its crystallization but also precipitation-during the chilling steps, it is necessary in the case offresidue stocks to decolorlze the oil by treating before subjecting it toa dewaidng process. In the case of steam or vacuum distillates, a portion oi the coloring material is separated during the fractionation inasmuch as these are overhead products. However, there is always present in these oils coloring material of the same boiling range as the oil distillate recovered. This amount of coloring material is generally too large and must be reduced before attempting to dewax. If the oils are dewaxed without attempting to remove'the coloring matter, it will be found that some of the wax has not been removed, due to the retarding-solyent gf.

These oils may be' treated by any of fect of the coloring material. After attempted dewaxing, when it is decolorized, the wax which has not been removed has been released. This i will be apparent by cloud test and will cause an,

increase in the pour test. I

This physical action is very marked when comparative tests of dewaxing results are made with light and dark samples of the same oil or if one sample is decolorized and the other material vpermitted to remain dark, both samples 'being processed inthe same manner for dewaxl ing. It will be found that the dark sample will give fictitious results as to cold test or apparent waxes. If the dark sample is subsequently finished to the same color as the light-or decolorized sample, it will be found that a large percentage of wax is held back by coloring matter.

O ils bearing amorphous waxes must be treated by special methods in order to accomplish dewaxing These oils are generally dewaxed by rst diluting with naphtha or some other suitable solvent, chilling the oil naphtha solution and f then separating by cold settling, centrifuging or by filter aid. l f

If the oil is completely decolorizedl before dewaxing, however, the ease of dewaxing is impaired. This. isdue to the fact that the presence ,of ccloring material tends to render the wax amorphous and it is with amorphous wax that the greatest shift in partition of a diluent-solvent is obtained. This shift is necessary in order to cause a dif ference in density between the wax and oil components at low temperatures. The diderence in density results due to the partition of the solvent shifting, the solvent leaving the wax and mov- `ing tothe oil. This shift in the solvent iscontrolled by the presence ofthe coloring material. or byf'actual form of the wax. That is, an excess of coloring material results Ain a predominance of amorphous wax which is dissolved by the coloringmaterial to such an extent that separation is diicult. f

It is obvious from the foregoing discussion that, .if the coloring matter is not removed fromthe oil, lit is impossible to obtain' complete dewaxing. Ii all of the coloring matter is removed from the oil, the formation of amorphous wax is retarded, preventing the greatest shift inpartition of the diluent-solvent and crystalline waxl ,predominatea and impairing the ease of dewaxing. I

One object of my invention is to provide a process of dewaxing by controllingthe formation of amorphous waxby the control of the concentration of the coloring material with coloring material.

Another object of my invention is to provide a process of dewaxing in which a uniform grade of wax is obtained.

Another object of my invention is to provide a combined process of dewaxing and decolorizing in which the decolorizing steps are carried out in a manner to aid the dewaxing operations.

A further object of my invention is to provide a process for dewaxing oils in which the advantage of the coloring material as a retarder is utilized in the early stages by retaining a portion thereof and completely decolorizing only after a wax separation has been effected.

A further object of my invention is to provide a combined decolorizing and dewaxing process in Which the decolorizing steps are carried out in two stages, one being physical and the second being chemical. Further objects of my invention will appear from the following specification.

The accompanying drawing is a diagrammatic chart showing one method of carrrying out the process of my invention and showing the steps comprising the process.

In general, my invention contemplates diluting a color-containing stock with a suitable solvent-diluent, chilling the oil solution to a temperature which will control the action of the treating agent in the treating step. After the oil solution has been chilled, I treat same with sulphuric acid or sulphur dioxide or-cther suitable treating agents such as phenols or the like; inasmuch as the oil has been chilled to the proper temperature, the action of the treating agent is a purely physical one, that is, the lower temperature prevents the chemical action of the treating agent with the coloring material, the effect of the treating agent being that of a solvent for the coloring only. Ii the oil solution is treated at normal temperatures, the first action oi. the treating agent will be that of a solvent dissolving the coloring matter. The dissolved colored matter will then react chemically with the treating agent and liberate other materials which will go back into solution in the original or treated oil. By cooling the solution, I limit the action of the sulphuric acid or sulphur dioxide to its solvent action. Certain of the coloring matter is insoluble and will not be dissolved out. The presence of this coloring matter, however, as set out above, is beneficial and aids in the ease of dewaxing by promoting the shifting of the solvent. After the acid sludge from this treating step is removed, the treated oil solution is then chilled to its dewaxing temperature and submitted to a dewaxing treatment such as is well known to the art, as centrifuging, cold settling, or by the use of a filter aid. The filtered and treated oil is then fully decolorized by the use of treating agents, the oil having been raised in temperature by heat exchange with the incoming oil so that the treating agent may excroise its chemical action.

More particularly, my process contemplates treating of a color bearing stock such as a crude residuum, vacuum distilled stock which is pea green in color, or a steam distilled stock which is olive green in color. The viscosity of these may range between 60 to 180 seconds at 210 F. I blend the stock with a diluentsolvent which may comprise for 'example 20% of 200 F. initial boiling point naphtha, 20% propane, and 60% of aoaaier the stock to be dewaxed. It is to be understood thatI do not wish to be limited to any particular diluent-solvent, the above being merely illustrative. I blend the diluent with the stock at a temperature of F. to 120 F. under pressures from to 200 pounds per square inch. After the blending step, I chill the solution by heat exchange or in any other suitable manner such as by evaporating propane, reducing the pressure on the system and drawing off the propane vapors, cooling to about 70 F. to 5 F., depending upon the stock being processed. At this temperature, the chemical action of treating agents is prevented. After the solution has been chilled, I mix thoroughly with sulphuric acid or sulphur dioxide; as pointed out above, the treating agents action is purely physical, being a solvent only at these temperatures. The acid sludge which is formed represents a solution of the coloring material in the treating agent. I withdraw this sludge and separate the acid therefrom before the temperature rises to prevent the chemical reaction between the coloring material and the acid so that I may recoverv the acid for reuse. The treated oil is then chilled to temperatures between -20 and -80 F. depending upon the cold test required. During this second chilling step, I may add more propane as a diluent if necessary. l

When the oil has reached its proper temperature, I dewax the solution by centrifuging, cold settling, or by the use of a filter aid, withdrawing the dewaxed oil solution and the wax or petrolatum solution separately. I pass the dewaXed oil solution in heat exchange in counterow relation to the incoming oil to raise the temperature of' the dewaxed oil solution and, at the same time, to chill the incoming oil to be treated. I recover the diluent-solvent from the dewaxed oil solution by distillation and subject the dewaxed oil to decolorizing treatment to remove the color materials and to obtain the final color. Similarly, I heat the Wax solution to recover the diluent and contact the wax for final color.

It will be appreciated that I have accomplished the objects of my invention. I am enabled, by controlling decolorizing, to increase the effectiveness of the dewaxing operation, my

process being in the nature of a combined treatu ing and dewaxing process.

It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is, therefore, to be understood that my invention is not to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

l. The processv of dewaxing hydrocarbon oils bearing a wax crystallization retarder in the form. of coloring material, including the steps of blending a diluent with the hydrocarbon oil, chilling the solution thus formed substantially to a temperature at which the retarding effect of the col- .oring material is overcome, removing such a portion of the coloring material that the wax crystallization retardation effect of the remainder will not prevent substantially complete wax precipitation on further chilling, sub-chilling the solution 7l to precipitate the wax and separating the wax from the solution.

2. A process for dewaxing hydrocarbon oils bearing a natural wax crystallization retarder in the form of coloring material including the steps of blending a diluent with the hydrocarbon oil, chilling the solution thus formed while the retarder prevents a substantial precipitation of wax to a temperature between 70 F. and 5 F., depending upon the hydrocarbon oil being treated, treating the solution thus chilled with an agent selected from the class consisting of sulphuric acid and sulphur dioxide, to remove a suflcient portion of the coloring material so that the retarding action thereof is substantially removed, sub-chilling the solution to precipitate the wax and dewaxing the oil.

3. In a process of dewaxing wax-bearing hydrocarbon oils containing a wax crystallization retarding coloring material, blending a solvent with the oil to form a solution of wax and oil in the solvent, chilling the solution thus formedv while the coloring material prevents a substan-y tial precipitation of wax to a temperature between 70 F. and 5 F., depending upon the hydrocarbon oil being treated, removing such a portion of the coloring material from the oil that the wax crystallization retardation eiect of the remainder will not prevent substantially complete wax precipitation on further, chilling, sub-chilling the solution to precipitate the wax and separating the precipitated wax from the solution. 4. In a process of dewaxing Wax-bearing hydrocarbon oils containing coloring material, blending a solvent with the oil to form a solution, chilling the solution to a temperature between 70 F. and a temperature not below that at which the retarding effect of the coloring material is substantially overcome, removing such temperature not below that at which the retarding effect of the coloring material is substantially overcome, removing such a portion of the coloring material from the oil that the wax crystallization retardation effect of the remainder will not prevent substantially complete wax precipitation on further chilling, adding solvent-diluent to the solution, sub-chilling the solution to precipitate the wax and removing the .precipitated wax from the oil.

EARL PE'I'I'Y.

DISCLAIMER 2,023,181.-Ea,rl Petty, Hempstead, N. Y. METHQD 0F DEWAXING HYDROCARBON OILS. Patent dated December 3, 1935. Disclaimer filed August 19, 1937, by the assignee, Sun Oil Company. Hereb enters this disclaimer to claim 1 in said Letters Patent.

[icial Gazette September 7, 1937.] 

